Apparatus for spray drying flowable liquid-containing material



May 10, 1960 B. E. BUDAHN APPARATUS FOR SPRAY DRYING FLOWABLELIQUID-CONTAINING MATERIAL 2 Sheets-Sheet 1 Filed Feb. 7, 1956 jzz/verzior' fime/ZZJW May 10, 1960 B. E. BUDAHN 2,936,029

APPARATUS FOR SPRAY DRYING FLOWABLE LIQUID-CONTAINING MATERIAL FiledFeb. 7, 1956 2 Sheets-Sheet 2 TIMING N Q Q Zizvemfar fmalz% m StatesAPPARATUS FOR SPRAY DRYING FLOWABLE LIQUID-CONTAINING MATERIAL BurneilE. Budahn, Bongards, Minn. Application February 7, 1956, Serial No.563,873

2 Claims. (Cl. 159-4) This invention relates to high capacity apparatusfor spray-drying material supplied in liquid, semi-liquid, emulsion andsolid-liquid mixture state.

This application is a continuation-in-part application of my priorapplication for patent, S.N. 159,908, filed by me May 4, 1950, nowabandoned, and entitled Apparatus For Spray-Drying FlowableLiquid-Containing Maten'als.

My invention is well adapted for manifold uses in spraydrying in theproduction of fine, granulated or powdered material, but is particularlywell adapted for the production of milk and buttermilk powders includingthe production of non-hygroscopic whey powders containing the stable ormonohydrate milk sugars. All previously known methods of forming a driedwhey product results in the production of a dried whey powder which isunstable and will revert back to the hygroscopic form over a period oftime. My invention eliminates this undesirable characteristic.

It is an object of my invention to provide simple and highly efficientapparatus for spray-drying materials of the class described, to producefinely divided granular or powdered products which may be controlledwithin close working limits and which will most effectively spray, airtreat, dry and collect the material treated and the resultant productrespectively.

Another object is to provide a novel method of spray drying whey toyield a stable non-hygroscopic whey powder.

A further object is the provision of apparatus of the class describedwherein a venturi action and high turbulence is produced in the sprayingand dispersion of the supplied material with attendant elimination ofdead spots in the spraying chamber and the elimination of all tendencyof the powdered product toback flow through the air supply ducts. Y

Another object is to provide spray-drying apparatus particularly adaptedfor high capacity commercial use wherein after spraying, air treatingand dispersion at optimum conditions, the powder formed is permitted toaccumulate and stand undisturbed for predetermined, desirable intervalsand then is removed at regular intervals from the bottom or lowerportion of the chamber.

A more specific object is the provision of spray-drying apparatus of theclass described wherein the nozzles or other discharge of the suppliedmixture containing liquid, are enveloped by a relatively large,- rapidvortex of hot air or other gas surrounding the discharge and dispersingand treating the sprayed product with optimum efiiciency. v A stillfurther object is the provision of powdered product-deflection andcollection which may be regulated in accordance to the specificrequirements and which closely cooperate with the product-removal meansto obtain highly efficient results and control.

These and other objects and advantages of my invention will more fullyappear from the following description made in connection with theaccompanying drawings 2,936,029 Patented May 10, 1960 wherein likereference characters refer to similar parts throughout the several viewsand in which:

Fig. l is a vertical section taken longitudinally through an embodimentof my spray-drying apparatus apex'along the line 1-1 of Fig. 2;

Fig. 2 is a horizontal section taken along the line 22 of Fig. 1;

Fig. 3 is a vertical cross section taken along the line 33 of Fig. 1looking toward the spray discharge nozzle;

Fig. 4 is a detail end elevation on a larger scale showing my novelmaterial-conveying element in operative material-moving position;

Fig. 5 is a similar view showing the conveying element in a feathered orreturn position; and

Fig. 6 is a detail front elevation showing the stationary mechanism forimparting a rapid vortex upon the discharged hot air.

In the form of the invention illustrated, a generally horizontallyextending drying chamber is utilized, comprising as shown, a verticalfront wall 10, a diminished rear wall 11, a flat bottom wall 12 declinedslightly from the rear to the front end of the enclosure and side walls13 and a top wall 14. The bottom wall 12 is preferably disposed somedistance above the floor of the building in which my apparatus ismounted, to facilitate accommodation of endless conveyor operatingchains or flexible elements 15. The walls of the drying enclosure orchamber are preferably constructed from concrete or suitable structuralmaterial or composition having good heat insulation properties. The roofor ceiling of the chamber, as shown, is substantially horizontalthroughout the portion thereof above the initial spraying action andtreatment of the material and then angles downwardly toward the rearwall 11 of the chamber to diminish the height of the chamber where thespray dried material is mainly collected and where the air used fordrying is exhausted from the chamber through suitable means such as awide air exhaust duct 16. v

In the front or intake wall 10 of the enclosure or chamber, I provideone or more spraying units, two thereof being shown in the embodimentillustrated. Each of said units comprises as shown, a relatively largecylindrical air emaust sleeve 17a connected as shown as an integral partof an elbow duct 17 which in the drawings, extends downwardly from thedelivery end of a heating chamber H which has mounted therein (notshown) suitable heating coils. The duct 17 from its communication withthe heating chamber H tapers downwardly into communication with itslower or discharge extremity 17a which is disposed approximately 5.75feet above the bottom wall 12.

Mounted in fixed relation to the hot air discharge sleeve 17a is afan-like air turbinating device 18 consisting in a plurality of fixedvanes or blades preferably of variable pitch construction, disposedradially of the axis of the discharge sleeve 17a and centrally recessedand if desired, secured at their inner ends to a tube 19 which isfixedly, but detachably mounted in the lower portion of duct 17 andwhich extends axially of the discharge sleeve 17a. Within tube 19 isshown a materialsupply conduit 20 of relatively small diameter,extending axially of tube 19 and having at its extremity, as shown,within the front of the spray chamber, a discharge nozzle 21 of a typepreferably to direct a conical spray of finely divided particles axiallyof the nozzle. The two spray units comprising the cooperating partsdescribed as shown in the form illustrated, are mounted medially in thefront wall of the enclosure defining the drying chain bet in widelyspaced relation and are directed substantially horizontally.

Hot air moved at high velocity is supplied to the upper enlarged end ofthe air duct 17 from the heater chamber or housing H by means of apowerful blower (not shown) enclosed within a blower casing B, thedischarge of which is in communication with the rear end of the heatingchamber H. I prefer to provide a suitable filter housing F at the rearof the blower having at its forward end communication with the blowerhousing and having suitable air intakes (not shown) at its rear end. Forconvenience, the filter unit, the blower housing and the heating chamberin the form disclosed, are supported upon the top of my drying andspraying chamber.

Extending transversely of the drying chamber is a pair of drag elementsindicated generally as 22 and comprised of an elongated plate member 23,the upper and lower edges of which are bent inwardly to form dry productengaging flanges 24. The drag elements 22 are secured to a plurality ofelongated flexible members by a pair of cable clamps 26 which aresecured to the flexible elements or cables 25 immediately fore and aftof the plate member 23 to secure the same thereto and to permit the sameto rock backwardly and forwardly thereon. Secured to the back of theplate 23 are a plurality of sliding elements or rockers 27 which engagethe bottom 12 of the drying chamber when the entire drag element 22 ismoved rearwardly. As best shown in Fig. 1, the cables 15 extend around aroller 28 which is secured to the end of the drying chamber adjacent theexhaust duct 16. These cables 15 also extend around a drive pulley 29which is mounted on a motor driven shaft 30. The motor 35 which providesthe power for driving the shaft 30 and the drive pulleys 29 is shown inFig. 2 and is of the reversible type which will cause the cable elements15 to move forwardly toward the drive pulley 29 a distance equal to thelength of the chamber and which will then cause the cable to moverearwardly to its original position and stop for a predeterminedinterval before moving again. I have found that it is preferable tospace the periods during which the cable elements are moved to aboutfive minute intervals. It is imperative that the material deposited onthe bottom wall 12 be permitted to remain in an undisturbed state atleast one minute. I have found that if this is done, the dried particleswill stabilize and will not revert to hygroscopic form upon standing. Inthe form shown herein, I utilize a 66-68 second cycle for thedischarging operation (about 33-34 seconds required for the movement ineach direction) and I repeat the operation about every five minutes. Aconventional timing switch mechanism 36 is illustrated as beingconnected to reversible motor 35. Timing switch 36 operates in a wellknown manner such that the motor is driven in a forward direction forapproximately 33 or 34 seconds to move the drag elements 22 from one endof the chamber to the other, whereupon the switch causes the motor to bedriven in the reverse direction for an additional 33 or 34 seconds so asto move the drag elements back to their original starting position. Theswitch then maintains the motor inactive for a period of approximatelyfour minutes and then again energizes the motor so as to complete acycle of movement of the drag elements. It is evident that the timingswitch may be adjusted so as to provide any time interval for theintermittent actuation of the conveyor means.

As best shown in Fig. 1 the bottom wall 12 of the drying chamber isprovided with a transverse opening adjacent its lower end in which ismounted a trough 31. Mounted in this opening for rotary movement is ananger type conveyor 32 which is driven by a motor (not shown) and whichis adapted to convey material to an elevator 33 disposed at one of itsends.

Depending from the top wall 14 of the drying chamber is a verticallyadjustable restricting element or curtain 34. This curtain is preferablyof stainless steel or some other material which will present a verysmooth nonadhering surface to the dried particles of material with whichit will come in contact. The interior surfaces of the drying chamber arealso preferably formed of a ma..-

4 terial which will present a smooth non-adhering surface to the driedparticles of material.

In operation, air is drawn from the outside through the filter housing Fby the blowers mounted in the blower housing B and forced thereby overthe heating coils in the heating chamber H and into the restricted elbowduct 17. From there the hot air is forced through the exhaust sleeve 17aand through the air turbinating device 18 and expelled at a very highvelocity into the drying chamber. It has been found that a volume in thevicinity of 8000 cu. ft. per minute discharged into the drying chamberin this manner is preferable. As this hot dry air is forced through theair turbinating device 18 a vortex of highly turbulent hot air isproduced which rushes inwardly into the chamber immediately beyond theinner end of the tube 19 and the discharge nozzle 21. This tube 19 asbest shown in Fig. 1 communicates with the outside air. The naturalresult of driving this high velocity vortex of hot air past the forwardend of the tube 19 is to draw in through the Venturi action which isthereby produced a relatively small supply of cool air. This cool air,of course, is immediately and uniformly distributed throughout thevortex as a direct result of the expansion which takes place when airunder compression is released and helps in the further comm-inution ofthe material spray particles discharged from nozzle 21.

Into the center of the vortex of hot and rapidly expanding air describedabove the fiowable liquid-containing materials are sprayed. This isaccomplished through the use of a pump (not shown) which is connected tothe material supply conduit 20. This pump forces the liquid-containingmaterials through the discharge nozzle 21 under considerable compressionso as to cause a substantially conical spray of the liquid-containingmaterial to be dis charged at the center of the vortex. The dischargenozzle 21 is preferably of a type which will cause the liquidcontainingmaterial to be finely divided into a multiplicity of minute particles.As these minute particles of liquidcontaining material are expelled intothe center of the vortex they are drawn outwardly in conjunction withthe expanding gases and thereby subjected to maximum impingement bymolecules of hot dry air. The turbulent nature of the gases insures thateach and every particle of the liquid-containing material will bebrought into contact with a maximum number of hot air molecules. Theseparticles are thus dried with substantially efliciency. When dried theyassume solid characteristics and the majority settle upon the bottom 12of the drying chamber.

As this process continues to operate, the warm air is, of course, forcedtoward the outlet end of the drying chamber and comes in contact withthe downwardly sloping ceiling and the adjustable steel curtain 34.These members direct the air downwardly so as to cause such driedparticles as have not as yet settled to the bottom 12 to be brought intocontact with the particles which have previously settled out of the air.It has been found that when a particle which is still moving through theair mass within the drying chamber comes into contact with particleswhich have already been deposited upon the bottom 12 the adhesiontherebetween is sufficient to retain the previously moving particles incontact with those previously deposited. Thus most of the dried wheyparticles settle adjacent the rear wall 11 of the chamber and very few,if any, settle adjacent the front wall 10. The curtain 34 may beadjusted to increase or decrease as is found necessary the extent towhich these particles are brought into the vicinity of the previouslydeposited material. As the relatively particle-free air moves beyond thecurtain 34 it is carried through the exhaust duct 16 to a dust collectorof the conventional type (not shown) where, if desired, the fewremaining particles suspended in the air may be collected.

7 After the dried particles of the liquid-containing material havesettled upon the bottom 12 sufficiently long to form a layer about oneinch thick, they are removed at regular intervals by the drag element22. I have found in the drying of flowable liquid-containing materials,that it is advantageous in drying the same to permit the accumulation ofthe dried product to continue for an interval, remaining undisturbed onthe bottom of the drying chamber, and to thereafter Withdraw it.Accordingly, at predetermined regular and relatively short intervals,the drag element 22 is promptly propelled from the upper end of thedrying chamber toward the opening 31 in which is located the trough. Asstated previously, I prefer to actuate or operate the drag element 22about every five minutes. It is possible to shorten that interval butcare must be exercised not to shorten this period below one minute forthe particles should remain undisturbed at least that long for properconversion into a stable state. I prefer to move the drag element 22 atsuch a speed that it requires 66-68 seconds to move from initialposition to discharge position and back again to initial position. Ithen keep the drag element immobile until about four additional minuteshave passed whereupon the drag element is again operated.

As the drag element moves forwardly the downwardly extending flanges 24engage the deposited dried product and carry it along therewith anddeposit it into the trough 31. The dried particles are piled, so tospeak, against and around the trough 31. Thereafter the dried product iscarried laterally by the auger type conveyor 32 into the elevator 33which deposits the same wherever desired for eventual packaging, storageor shipment. As indicated above, the drag element 22 is thereaftercaused by the drive roller 29 to move rearward ly to the upper end ofthe drying chamber and stopped for the short interval above mentioned(about four minutes).

As the drag element moves rearwardly the rockers 27 engage the bottom 12of the drying chamber and cause the drag element 22 to move from theposition shown in Fig. 4 to the feathered position shown in Fig. 5. Whenit is again moved forwardly after said interval, it is obvious that thelower flange 24 will again be brought down into contact with the driedproduct and will engage the same.

My apparatus is especially well adapted as described above for thedrying of fiowable liquid-containing materials. It provides a maximummixing of the molecules of finely divided particles of the material withturbulent hot air to prevent the possible settling of these particles ortheir joinder with each other before they are dried. The outwardflinging of these particles caused by the turbulent hot air in theaforementioned vortex insures an extremely rapid distribution of theparticles throughout the chamber. At the same time it insures theimpingement of these particles with a maximum number of molecules of hotair. My apparatus is capable and is especially Well adapted foroperation where it is necessary that the drying be performed underprecisely controlled conditions. This is especially true with respect tocontrol temperatures.

The utilization of a vortex of hot dry air in conjunction with theVenturi action is especially effective in the prevention of theformation of dead spots within the various portions of the dryingchamber. I have found that unless such a means is used to insure aturbulent flow of air that dead spots will form within the dryingchamber with the result that the drying operation within such areas isrelatively ineffective. I have also found that if an ordinary flow ofhot air without turbulence or vorticity is utilized, the Venturi actionis not suflicient to reduce the pressure at the nozzle below atmosphere,and there is a tendency for a back flow of the dried particles ofmaterial into the interior of the exhaust sleeve 17a and no aspirationof cool air through the tube 19. This, of .course, is extremelyundesirable and is prevented with my apparatus through the utilizationof the turbinating device 18 which forms the sufiiciently high velocityvortex without increasing the rate of mass flow into the drying chamberto build up a back pressure therein.

I have found that in the production of dried materials such as hereindescribed it is advantageous to permit the dried particles which settleupon the bottom 12 of the drying chamber to remain thereon for a shortperiod of time before their removal in order to enable the formation ofthe monohydrate form of the dried particles adjacent the bottom and theabsorption by them of only sufiicient heat to complete a similarformation of the rest of the particles above them after removal. Toaccomplish this and to make the product uniform, I have utilized thedrag elements 22 in conjunction with the cables 15 and the drive rollers29 which are operated and stopped at predetermined regular intervals toinsure that all of the material will be permitted to remain undisturbedupon the bottom 12 for at least the required short period of time (aboutone minute) and to insure that none of the material will remain thereonfor too long a period of time. This interval timing is critical, becauseif too short, not all of it will reach the monohydrate form, which isthe most stable non-hygroscopic form of the dried material.

My apparatus is especially well adapted to the drying of whey productsand similar liquid-containing materials. It has been found that if Wheyis dried under optimum conditions the stable monohydrate form will beproduced. This form is the desired form, since it is both stable andnon-hygroscopic and consequently is not sticky. We have found that inthe particular apparatus illustrated here, if we introduce hot air witha temperature in the neighborhood of 300 F. adjacent the air turbinatingdevice 18 and if we adjust the curtain 34 so as to provide atemperature'adjacent it in the neighborhood of 160 F. and a temperatureadjacent the duct 16 in the neighborhood of F. substantially all of thewhey particles will assume a desired solid form. The rapid dis tributionof the particles of whey throughout the air chamber by the vortex of hotair is of particular importance in subjecting the various particles ofwhey to substantially the same conditions throughout the chamber. Thisinsures a relatively uniform dried product, a characteristic highlydesirable in any drying operation of whey. However, this solid form,though non-hygroscopic, is unstable unless permitted to remainundisturbed for the required period of time and will revert back to thehygroscopic form which is a highly undesirable product.

It will, of course, be understood that various changes may be made inthe form, details, arrangement and proportions of the various partswithout departing from the scope of my invention.

What is claimed is:

1. In an apparatus for drying flowable liquid-containing material suchas whey, a drying chamber having a bottom wall and having first andsecond sidewalls disposed opposite each other, means at said firstsidewall for continuously introducing such fiowable material into saidchamber in a substantially horizontal direction and toward the secondsidewall and said means effecting deposit of material upon the bottomwall in a mass of temporarily relatively stationary, partially driedparticles which remain stationary in the chamber until substantiallycompletely dried, means at the bottom wall and adjacent said first wallfor discharging material from the chamber, a scraper on the bottom walland normally disposed in stationary position adjacent said secondsidewall, means mounting the scraper for movement back and forth betweensaid first and second sidewalls and adjacent the bottom and formaintainig the scraper in scraping relation with the bottom when movedtoward said first sidewall, and means periodically cycling the scraperfirst forwardly toward said first sidewall and then back along thebottom wall to said second sidewall and maintaining the scraper instationary condition adjacent the second sidewall for a predeterminedinterval, where- 7 by to allow the particles to remain in a quiescentstate whereupon such materials as dried whey product will convert to anon-hygroscopic state.

2. In'an apparatus for drying flowable liquid-containing materials suchas whey, a drying chamber having a heat-insulating bottom wall and firstand second sidewalls disposed opposite each other, means at said firstsidewall for introducing such flowable material into the chamber in asubstantially horizontal direction and toward the second sidewall andsaid means effecting deposit of heated material upon the bottom wall ina of temporarily relatively stationary, partially dried particles whichremain stationary in the chamber until substantially completely dried,means at the bottom wall adjacent said first wall for dischargingmaterial from the chamber, a scraper on the bottom wall and normallydisposed in stationary position adjacent said second sidewall, meansmounting the scraper for movement back and forth between said first andsecond sidewalls and adjacent the bottom and for maintaining the scraperin scraping relation with the bottom when moved toward said firstsidewall, and means periodically, cycling the scraper forwardly towardsaid first sidewall and then back along the bottom to' said second walland maintaining the scraper in stationary condition adjacent the second8 sidewall fora predetermined interval, whereby the quiescent state ofsuch materials, along with the heated condition of the particles and themutual heat provided between adjacent particles effects conversionof theproduct to a non-hygroscopic state.

References Cited in the file of this patent UNITED STATES PATENTS1,088,436 Merrell Feb. 24, 1914 1,537,060 Beardslee May 12, 19251,542,939 Hopkins June 23, 1925 1,723,880 Paltzer Aug. 6, 1929 1,754,941Frohring et al. Apr. 15, 1930 1,928,135 Peebles Sept. 26, 1933 1,959,301Northcutt et al May 15, 1934 1,984,381 Peebles Dec. 18, 1934 2,110,167Northcutt et a1 Mar. 8, 1938 2,188,506 Hall Jan. 30, 1940 2,552,743Simpson May 15, 1951 2,815,071 Hensley et al. Dec. 3, 1957 OTHERREFERENCES Food & Food Products, by Morris B. Jacobs, vol. II, 2nd. ed.,pp. 892, 893, 1543, Interscience Publishers, Inc. N. Y.

